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|
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
<title>pugixml 0.9</title>
<link rel="stylesheet" href="pugixml.css" type="text/css">
<meta name="generator" content="DocBook XSL Stylesheets V1.75.2">
<link rel="home" href="quickstart.html" title="pugixml 0.9">
</head>
<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
<div class="article">
<div class="section">
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="quickstart.main"></a><a class="link" href="quickstart.html#quickstart.main" title="pugixml 0.9 quick start guide"> pugixml 0.9 quick start guide</a>
</h2></div></div></div>
<div class="toc"><dl>
<dt><span class="section"><a href="quickstart.html#quickstart.main.introduction"> Introduction</a></span></dt>
<dt><span class="section"><a href="quickstart.html#quickstart.main.install"> Installation</a></span></dt>
<dt><span class="section"><a href="quickstart.html#quickstart.main.dom"> Document object model</a></span></dt>
<dt><span class="section"><a href="quickstart.html#quickstart.main.loading"> Loading document</a></span></dt>
<dt><span class="section"><a href="quickstart.html#quickstart.main.access"> Accessing document data</a></span></dt>
<dt><span class="section"><a href="quickstart.html#quickstart.main.modify"> Modifying document data</a></span></dt>
<dt><span class="section"><a href="quickstart.html#quickstart.main.saving"> Saving document</a></span></dt>
<dt><span class="section"><a href="quickstart.html#quickstart.main.feedback"> Feedback</a></span></dt>
<dt><span class="section"><a href="quickstart.html#quickstart.main.license"> License</a></span></dt>
</dl></div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="quickstart.main.introduction"></a><a class="link" href="quickstart.html#quickstart.main.introduction" title="Introduction"> Introduction</a>
</h3></div></div></div>
<p>
pugixml is a light-weight C++ XML processing library. It consists of a DOM-like
interface with rich traversal/modification capabilities, an extremely fast
XML parser which constructs the DOM tree from an XML file/buffer, and an
XPath 1.0 implementation for complex data-driven tree queries. Full Unicode
support is also available, with Unicode interface variants and conversions
between different Unicode encodings (which happen automatically during parsing/saving).
The library is extremely portable and easy to integrate and use. pugixml
is developed and maintained since 2006 and has many users. All code is distributed
under the MIT license, making it completely free to use in both open-source
and proprietary applications.
</p>
<p>
pugixml enables very fast, convenient and memory-efficient XML document processing.
However, since pugixml has a DOM parser, it can't process XML documents that
do not fit in memory; also the parser is a non-validating one, so if you
need DTD/Schema validation, the library is not for you.
</p>
<p>
This is the quick start guide for pugixml, which purpose is to enable you
to start using the library quickly. Many important library features are either
not described at all or only mentioned briefly; for more complete information
you <a href="manual.html" target="_top">should read the complete manual</a>.
</p>
<div class="note"><table border="0" summary="Note">
<tr>
<td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="images/note.png"></td>
<th align="left">Note</th>
</tr>
<tr><td align="left" valign="top"><p>
No documentation is perfect, neither is this one. If you encounter a description
that is unclear, please file an issue as described in <a class="xref" href="quickstart.html#quickstart.main.feedback" title="Feedback"> Feedback</a>. Also if
you can spare the time for a full proof-reading, including spelling and
grammar, that would be great! Please <a class="link" href="quickstart.html#email">send me an e-mail</a>;
as a token of appreciation, your name will be included into the corresponding
section of the manual.
</p></td></tr>
</table></div>
</div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="quickstart.main.install"></a><a class="link" href="quickstart.html#quickstart.main.install" title="Installation"> Installation</a>
</h3></div></div></div>
<p>
pugixml is distributed in source form. You can download a source distribution
via one of the following links:
</p>
<pre class="programlisting"><a href="http://pugixml.googlecode.com/files/pugixml-0.9.zip" target="_top">http://pugixml.googlecode.com/files/pugixml-0.9.zip</a>
<a href="http://pugixml.googlecode.com/files/pugixml-0.9.tar.gz" target="_top">http://pugixml.googlecode.com/files/pugixml-0.9.tar.gz</a>
</pre>
<p>
The distribution contains library source, documentation (the guide you're
reading now and the manual) and some code examples. After downloading the
distribution, install pugixml by extracting all files from the compressed
archive.
</p>
<p>
The complete pugixml source consists of four files - two source files, <code class="filename">pugixml.cpp</code> and
<code class="filename">pugixpath.cpp</code>, and two header files, <code class="filename">pugixml.hpp</code> and <code class="filename">pugiconfig.hpp</code>. <code class="filename">pugixml.hpp</code> is
the primary header which you need to include in order to use pugixml classes/functions.
The rest of this guide assumes that <code class="filename">pugixml.hpp</code> is either in the current directory
or in one of include directories of your projects, so that <code class="computeroutput"><span class="preprocessor">#include</span> <span class="string">"pugixml.hpp"</span></code>
can find the header; however you can also use relative path (i.e. <code class="computeroutput"><span class="preprocessor">#include</span> <span class="string">"../libs/pugixml/src/pugixml.hpp"</span></code>)
or include directory-relative path (i.e. <code class="computeroutput"><span class="preprocessor">#include</span>
<span class="special"><</span><span class="identifier">xml</span><span class="special">/</span><span class="identifier">thirdparty</span><span class="special">/</span><span class="identifier">pugixml</span><span class="special">/</span><span class="identifier">src</span><span class="special">/</span><span class="identifier">pugixml</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span></code>).
</p>
<p>
The easiest way to build pugixml is to compile two source files, <code class="filename">pugixml.cpp</code> and
<code class="filename">pugixpath.cpp</code>, along with the existing library/executable. This process depends
on the method of building your application; for example, if you're using
Microsoft Visual Studio<sup>[<a name="trademarks" href="#ftn.trademarks" class="footnote">1</a>]</sup>, Apple Xcode, Code::Blocks or any other IDE, just add
<code class="filename">pugixml.cpp</code> and <code class="filename">pugixpath.cpp</code> to one of your projects. There are other building
methods available, including building pugixml as a standalone static/shared
library; read the manual for further information.
</p>
</div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="quickstart.main.dom"></a><a class="link" href="quickstart.html#quickstart.main.dom" title="Document object model"> Document object model</a>
</h3></div></div></div>
<p>
pugixml stores XML data in DOM-like way: the entire XML document (both document
structure and element data) is stored in memory as a tree. The tree can be
loaded from character stream (file, string, C++ I/O stream), then traversed
via special API or XPath expressions. The whole tree is mutable: both node
structure and node/attribute data can be changed at any time. Finally, the
result of document transformations can be saved to a character stream (file,
C++ I/O stream or custom transport).
</p>
<p>
The root of the tree is the document itself, which corresponds to C++ type
<code class="computeroutput"><span class="identifier">xml_document</span></code>. Document has
one or more child nodes, which correspond to C++ type <code class="computeroutput"><span class="identifier">xml_node</span></code>.
Nodes have different types; depending on a type, a node can have a collection
of child nodes, a collection of attributes, which correspond to C++ type
<code class="computeroutput"><span class="identifier">xml_attribute</span></code>, and some additional
data (i.e. name).
</p>
<p>
The most common node types are:
</p>
<div class="itemizedlist"><ul class="itemizedlist" type="disc">
<li class="listitem">
Document node (<code class="computeroutput"><span class="identifier">node_document</span></code>)
- this is the root of the tree, which consists of several child nodes.
This node corresponds to <code class="computeroutput"><span class="identifier">xml_document</span></code>
class; note that <code class="computeroutput"><span class="identifier">xml_document</span></code>
is a sub-class of <code class="computeroutput"><span class="identifier">xml_node</span></code>,
so the entire node interface is also available.
</li>
<li class="listitem">
Element/tag node (<code class="computeroutput"><span class="identifier">node_element</span></code>)
- this is the most common type of node, which represents XML elements.
Element nodes have a name, a collection of attributes and a collection
of child nodes (both of which may be empty). The attribute is a simple
name/value pair.
</li>
<li class="listitem">
Plain character data nodes (<code class="computeroutput"><span class="identifier">node_pcdata</span></code>)
represent plain text in XML. PCDATA nodes have a value, but do not have
name or children/attributes. Note that plain character data is not a
part of the element node but instead has its own node; for example, an
element node can have several child PCDATA nodes.
</li>
</ul></div>
<p>
Despite the fact that there are several node types, there are only three
C++ types representing the tree (<code class="computeroutput"><span class="identifier">xml_document</span></code>,
<code class="computeroutput"><span class="identifier">xml_node</span></code>, <code class="computeroutput"><span class="identifier">xml_attribute</span></code>);
some operations on <code class="computeroutput"><span class="identifier">xml_node</span></code>
are only valid for certain node types. They are described below.
</p>
<div class="note"><table border="0" summary="Note">
<tr>
<td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="images/note.png"></td>
<th align="left">Note</th>
</tr>
<tr><td align="left" valign="top"><p>
All pugixml classes and functions are located in <code class="computeroutput"><span class="identifier">pugi</span></code>
namespace; you have to either use explicit name qualification (i.e. <code class="computeroutput"><span class="identifier">pugi</span><span class="special">::</span><span class="identifier">xml_node</span></code>), or to gain access to relevant
symbols via <code class="computeroutput"><span class="keyword">using</span></code> directive
(i.e. <code class="computeroutput"><span class="keyword">using</span> <span class="identifier">pugi</span><span class="special">::</span><span class="identifier">xml_node</span><span class="special">;</span></code> or <code class="computeroutput"><span class="keyword">using</span>
<span class="keyword">namespace</span> <span class="identifier">pugi</span><span class="special">;</span></code>).
</p></td></tr>
</table></div>
<p>
<code class="computeroutput"><span class="identifier">xml_document</span></code> is the owner
of the entire document structure; destroying the document destroys the whole
tree. The interface of <code class="computeroutput"><span class="identifier">xml_document</span></code>
consists of loading functions, saving functions and the interface of <code class="computeroutput"><span class="identifier">xml_node</span></code>, which allows for document inspection
and/or modification. Note that while <code class="computeroutput"><span class="identifier">xml_document</span></code>
is a sub-class of <code class="computeroutput"><span class="identifier">xml_node</span></code>,
<code class="computeroutput"><span class="identifier">xml_node</span></code> is not a polymorphic
type; the inheritance is only used to simplify usage.
</p>
<p>
<code class="computeroutput"><span class="identifier">xml_node</span></code> is the handle to
document node; it can point to any node in the document, including document
itself. There is a common interface for nodes of all types. Note that <code class="computeroutput"><span class="identifier">xml_node</span></code> is only a handle to the actual
node, not the node itself - you can have several <code class="computeroutput"><span class="identifier">xml_node</span></code>
handles pointing to the same underlying object. Destroying <code class="computeroutput"><span class="identifier">xml_node</span></code> handle does not destroy the node
and does not remove it from the tree.
</p>
<p>
There is a special value of <code class="computeroutput"><span class="identifier">xml_node</span></code>
type, known as null node or empty node. It does not correspond to any node
in any document, and thus resembles null pointer. However, all operations
are defined on empty nodes; generally the operations don't do anything and
return empty nodes/attributes or empty strings as their result. This is useful
for chaining calls; i.e. you can get the grandparent of a node like so:
<code class="computeroutput"><span class="identifier">node</span><span class="special">.</span><span class="identifier">parent</span><span class="special">().</span><span class="identifier">parent</span><span class="special">()</span></code>;
if a node is a null node or it does not have a parent, the first <code class="computeroutput"><span class="identifier">parent</span><span class="special">()</span></code>
call returns null node; the second <code class="computeroutput"><span class="identifier">parent</span><span class="special">()</span></code> call then also returns null node, so you
don't have to check for errors twice. You can test if a handle is null via
implicit boolean cast: <code class="computeroutput"><span class="keyword">if</span> <span class="special">(</span><span class="identifier">node</span><span class="special">)</span> <span class="special">{</span> <span class="special">...</span> <span class="special">}</span></code>
or <code class="computeroutput"><span class="keyword">if</span> <span class="special">(!</span><span class="identifier">node</span><span class="special">)</span> <span class="special">{</span> <span class="special">...</span> <span class="special">}</span></code>.
</p>
<p>
<code class="computeroutput"><span class="identifier">xml_attribute</span></code> is the handle
to an XML attribute; it has the same semantics as <code class="computeroutput"><span class="identifier">xml_node</span></code>,
i.e. there can be several <code class="computeroutput"><span class="identifier">xml_attribute</span></code>
handles pointing to the same underlying object, there is a special null attribute
value, which propagates to function results.
</p>
<p>
There are two choices of interface and internal representation when configuring
pugixml: you can either choose the UTF-8 (also called char) interface or
UTF-16/32 (also called wchar_t) one. The choice is controlled via <code class="computeroutput"><span class="identifier">PUGIXML_WCHAR_MODE</span></code> define; you can set
it via <code class="filename">pugiconfig.hpp</code> or via preprocessor options. All tree functions that
work with strings work with either C-style null terminated strings or STL
strings of the selected character type. Read the manual for additional information
on Unicode interface.
</p>
</div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="quickstart.main.loading"></a><a class="link" href="quickstart.html#quickstart.main.loading" title="Loading document"> Loading document</a>
</h3></div></div></div>
<p>
pugixml provides several functions for loading XML data from various places
- files, C++ iostreams, memory buffers. All functions use an extremely fast
non-validating parser. This parser is not fully W3C conformant - it can load
any valid XML document, but does not perform some well-formedness checks.
While considerable effort is made to reject invalid XML documents, some validation
is not performed because of performance reasons. XML data is always converted
to internal character format before parsing. pugixml supports all popular
Unicode encodings (UTF-8, UTF-16 (big and little endian), UTF-32 (big and
little endian); UCS-2 is naturally supported since it's a strict subset of
UTF-16) and handles all encoding conversions automatically.
</p>
<p>
The most common source of XML data is files; pugixml provides a separate
function for loading XML document from file. This function accepts file path
as its first argument, and also two optional arguments, which specify parsing
options and input data encoding, which are described in the manual.
</p>
<p>
This is an example of loading XML document from file (<a href="samples/load_file.cpp" target="_top">samples/load_file.cpp</a>):
</p>
<p>
</p>
<pre class="programlisting"><span class="identifier">pugi</span><span class="special">::</span><span class="identifier">xml_document</span> <span class="identifier">doc</span><span class="special">;</span>
<span class="identifier">pugi</span><span class="special">::</span><span class="identifier">xml_parse_result</span> <span class="identifier">result</span> <span class="special">=</span> <span class="identifier">doc</span><span class="special">.</span><span class="identifier">load_file</span><span class="special">(</span><span class="string">"tree.xml"</span><span class="special">);</span>
<span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"Load result: "</span> <span class="special"><<</span> <span class="identifier">result</span><span class="special">.</span><span class="identifier">description</span><span class="special">()</span> <span class="special"><<</span> <span class="string">", mesh name: "</span> <span class="special"><<</span> <span class="identifier">doc</span><span class="special">.</span><span class="identifier">child</span><span class="special">(</span><span class="string">"mesh"</span><span class="special">).</span><span class="identifier">attribute</span><span class="special">(</span><span class="string">"name"</span><span class="special">).</span><span class="identifier">value</span><span class="special">()</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span>
</pre>
<p>
</p>
<p>
<code class="computeroutput"><span class="identifier">load_file</span></code>, as well as other
loading functions, destroys the existing document tree and then tries to
load the new tree from the specified file. The result of the operation is
returned in an <code class="computeroutput"><span class="identifier">xml_parse_result</span></code>
object; this object contains the operation status, and the related information
(i.e. last successfully parsed position in the input file, if parsing fails).
</p>
<p>
Parsing result object can be implicitly converted to <code class="computeroutput"><span class="keyword">bool</span></code>;
if you do not want to handle parsing errors thoroughly, you can just check
the return value of load functions as if it was a <code class="computeroutput"><span class="keyword">bool</span></code>:
<code class="computeroutput"><span class="keyword">if</span> <span class="special">(</span><span class="identifier">doc</span><span class="special">.</span><span class="identifier">load_file</span><span class="special">(</span><span class="string">"file.xml"</span><span class="special">))</span> <span class="special">{</span> <span class="special">...</span>
<span class="special">}</span> <span class="keyword">else</span> <span class="special">{</span> <span class="special">...</span> <span class="special">}</span></code>.
Otherwise you can use the <code class="computeroutput"><span class="identifier">status</span></code>
member to get parsing status, or the <code class="computeroutput"><span class="identifier">description</span><span class="special">()</span></code> member function to get the status in a
string form.
</p>
<p>
This is an example of handling loading errors (<a href="samples/load_error_handling.cpp" target="_top">samples/load_error_handling.cpp</a>):
</p>
<p>
</p>
<pre class="programlisting"><span class="identifier">pugi</span><span class="special">::</span><span class="identifier">xml_document</span> <span class="identifier">doc</span><span class="special">;</span>
<span class="identifier">pugi</span><span class="special">::</span><span class="identifier">xml_parse_result</span> <span class="identifier">result</span> <span class="special">=</span> <span class="identifier">doc</span><span class="special">.</span><span class="identifier">load</span><span class="special">(</span><span class="identifier">source</span><span class="special">);</span>
<span class="keyword">if</span> <span class="special">(</span><span class="identifier">result</span><span class="special">)</span>
<span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"XML ["</span> <span class="special"><<</span> <span class="identifier">source</span> <span class="special"><<</span> <span class="string">"] parsed without errors, attr value: ["</span> <span class="special"><<</span> <span class="identifier">doc</span><span class="special">.</span><span class="identifier">child</span><span class="special">(</span><span class="string">"node"</span><span class="special">).</span><span class="identifier">attribute</span><span class="special">(</span><span class="string">"attr"</span><span class="special">).</span><span class="identifier">value</span><span class="special">()</span> <span class="special"><<</span> <span class="string">"]\n\n"</span><span class="special">;</span>
<span class="keyword">else</span>
<span class="special">{</span>
<span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"XML ["</span> <span class="special"><<</span> <span class="identifier">source</span> <span class="special"><<</span> <span class="string">"] parsed with errors, attr value: ["</span> <span class="special"><<</span> <span class="identifier">doc</span><span class="special">.</span><span class="identifier">child</span><span class="special">(</span><span class="string">"node"</span><span class="special">).</span><span class="identifier">attribute</span><span class="special">(</span><span class="string">"attr"</span><span class="special">).</span><span class="identifier">value</span><span class="special">()</span> <span class="special"><<</span> <span class="string">"]\n"</span><span class="special">;</span>
<span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"Error description: "</span> <span class="special"><<</span> <span class="identifier">result</span><span class="special">.</span><span class="identifier">description</span><span class="special">()</span> <span class="special"><<</span> <span class="string">"\n"</span><span class="special">;</span>
<span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"Error offset: "</span> <span class="special"><<</span> <span class="identifier">result</span><span class="special">.</span><span class="identifier">offset</span> <span class="special"><<</span> <span class="string">" (error at [..."</span> <span class="special"><<</span> <span class="special">(</span><span class="identifier">source</span> <span class="special">+</span> <span class="identifier">result</span><span class="special">.</span><span class="identifier">offset</span><span class="special">)</span> <span class="special"><<</span> <span class="string">"]\n\n"</span><span class="special">;</span>
<span class="special">}</span>
</pre>
<p>
</p>
<p>
Sometimes XML data should be loaded from some other source than file, i.e.
HTTP URL; also you may want to load XML data from file using non-standard
functions, i.e. to use your virtual file system facilities or to load XML
from gzip-compressed files. These scenarios either require loading document
from memory, in which case you should prepare a contiguous memory block with
all XML data and to pass it to one of buffer loading functions, or loading
document from C++ IOstream, in which case you should provide an object which
implements <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">istream</span></code> or <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">wistream</span></code>
interface.
</p>
<p>
There are different functions for loading document from memory; they treat
the passed buffer as either an immutable one (<code class="computeroutput"><span class="identifier">load_buffer</span></code>),
a mutable buffer which is owned by the caller (<code class="computeroutput"><span class="identifier">load_buffer_inplace</span></code>),
or a mutable buffer which ownership belongs to pugixml (<code class="computeroutput"><span class="identifier">load_buffer_inplace_own</span></code>).
There is also a simple helper function, <code class="computeroutput"><span class="identifier">xml_document</span><span class="special">::</span><span class="identifier">load</span></code>,
for cases when you want to load the XML document from null-terminated character
string.
</p>
<p>
This is an example of loading XML document from memory using one of these
functions (<a href="samples/load_memory.cpp" target="_top">samples/load_memory.cpp</a>);
read the sample code for more examples:
</p>
<p>
</p>
<pre class="programlisting"><span class="keyword">const</span> <span class="keyword">char</span> <span class="identifier">source</span><span class="special">[]</span> <span class="special">=</span> <span class="string">"<mesh name='sphere'><bounds>0 0 1 1</bounds></mesh>"</span><span class="special">;</span>
<span class="identifier">size_t</span> <span class="identifier">size</span> <span class="special">=</span> <span class="keyword">sizeof</span><span class="special">(</span><span class="identifier">source</span><span class="special">);</span>
</pre>
<p>
</p>
<p>
</p>
<pre class="programlisting"><span class="comment">// You can use load_buffer_inplace to load document from mutable memory block; the block's lifetime must exceed that of document
</span><span class="keyword">char</span><span class="special">*</span> <span class="identifier">buffer</span> <span class="special">=</span> <span class="keyword">new</span> <span class="keyword">char</span><span class="special">[</span><span class="identifier">size</span><span class="special">];</span>
<span class="identifier">memcpy</span><span class="special">(</span><span class="identifier">buffer</span><span class="special">,</span> <span class="identifier">source</span><span class="special">,</span> <span class="identifier">size</span><span class="special">);</span>
<span class="comment">// The block can be allocated by any method; the block is modified during parsing
</span><span class="identifier">pugi</span><span class="special">::</span><span class="identifier">xml_parse_result</span> <span class="identifier">result</span> <span class="special">=</span> <span class="identifier">doc</span><span class="special">.</span><span class="identifier">load_buffer_inplace</span><span class="special">(</span><span class="identifier">buffer</span><span class="special">,</span> <span class="identifier">size</span><span class="special">);</span>
<span class="comment">// You have to destroy the block yourself after the document is no longer used
</span><span class="keyword">delete</span><span class="special">[]</span> <span class="identifier">buffer</span><span class="special">;</span>
</pre>
<p>
</p>
<p>
This is a simple example of loading XML document from file using streams
(<a href="samples/load_stream.cpp" target="_top">samples/load_stream.cpp</a>); read
the sample code for more complex examples involving wide streams and locales:
</p>
<p>
</p>
<pre class="programlisting"><span class="identifier">std</span><span class="special">::</span><span class="identifier">ifstream</span> <span class="identifier">stream</span><span class="special">(</span><span class="string">"weekly-utf-8.xml"</span><span class="special">);</span>
<span class="identifier">pugi</span><span class="special">::</span><span class="identifier">xml_parse_result</span> <span class="identifier">result</span> <span class="special">=</span> <span class="identifier">doc</span><span class="special">.</span><span class="identifier">load</span><span class="special">(</span><span class="identifier">stream</span><span class="special">);</span>
</pre>
<p>
</p>
</div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="quickstart.main.access"></a><a class="link" href="quickstart.html#quickstart.main.access" title="Accessing document data"> Accessing document data</a>
</h3></div></div></div>
<p>
pugixml features an extensive interface for getting various types of data
from the document and for traversing the document. You can use various accessors
to get node/attribute data, you can traverse the child node/attribute lists
via accessors or iterators, you can do depth-first traversals with <code class="computeroutput"><span class="identifier">xml_tree_walker</span></code> objects, and you can use
XPath for complex data-driven queries.
</p>
<p>
You can get node or attribute name via <code class="computeroutput"><span class="identifier">name</span><span class="special">()</span></code> accessor, and value via <code class="computeroutput"><span class="identifier">value</span><span class="special">()</span></code> accessor. Note that both functions never
return null pointers - they either return a string with the relevant content,
or an empty string if name/value is absent or if the handle is null. Also
there are two notable things for reading values:
</p>
<div class="itemizedlist"><ul class="itemizedlist" type="disc">
<li class="listitem">
It is common to store data as text contents of some node - i.e. <code class="computeroutput"><span class="special"><</span><span class="identifier">node</span><span class="special">><</span><span class="identifier">description</span><span class="special">></span><span class="identifier">This</span>
<span class="identifier">is</span> <span class="identifier">a</span>
<span class="identifier">node</span><span class="special"></</span><span class="identifier">description</span><span class="special">></</span><span class="identifier">node</span><span class="special">></span></code>.
In this case, <code class="computeroutput"><span class="special"><</span><span class="identifier">description</span><span class="special">></span></code> node does not have a value, but instead
has a child of type <code class="computeroutput"><span class="identifier">node_pcdata</span></code>
with value <code class="computeroutput"><span class="string">"This is a node"</span></code>.
pugixml provides <code class="computeroutput"><span class="identifier">child_value</span><span class="special">()</span></code> helper functions to parse such data.
</li>
<li class="listitem">
In many cases attribute values have types that are not strings - i.e.
an attribute may always contain values that should be treated as integers,
despite the fact that they are represented as strings in XML. pugixml
provides several accessors that convert attribute value to some other
type.
</li>
</ul></div>
<p>
This is an example of using these functions (<a href="samples/traverse_base.cpp" target="_top">samples/traverse_base.cpp</a>):
</p>
<p>
</p>
<pre class="programlisting"><span class="keyword">for</span> <span class="special">(</span><span class="identifier">pugi</span><span class="special">::</span><span class="identifier">xml_node</span> <span class="identifier">tool</span> <span class="special">=</span> <span class="identifier">tools</span><span class="special">.</span><span class="identifier">child</span><span class="special">(</span><span class="string">"Tool"</span><span class="special">);</span> <span class="identifier">tool</span><span class="special">;</span> <span class="identifier">tool</span> <span class="special">=</span> <span class="identifier">tool</span><span class="special">.</span><span class="identifier">next_sibling</span><span class="special">(</span><span class="string">"Tool"</span><span class="special">))</span>
<span class="special">{</span>
<span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"Tool "</span> <span class="special"><<</span> <span class="identifier">tool</span><span class="special">.</span><span class="identifier">attribute</span><span class="special">(</span><span class="string">"Filename"</span><span class="special">).</span><span class="identifier">value</span><span class="special">();</span>
<span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">": AllowRemote "</span> <span class="special"><<</span> <span class="identifier">tool</span><span class="special">.</span><span class="identifier">attribute</span><span class="special">(</span><span class="string">"AllowRemote"</span><span class="special">).</span><span class="identifier">as_bool</span><span class="special">();</span>
<span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">", Timeout "</span> <span class="special"><<</span> <span class="identifier">tool</span><span class="special">.</span><span class="identifier">attribute</span><span class="special">(</span><span class="string">"Timeout"</span><span class="special">).</span><span class="identifier">as_int</span><span class="special">();</span>
<span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">", Description '"</span> <span class="special"><<</span> <span class="identifier">tool</span><span class="special">.</span><span class="identifier">child_value</span><span class="special">(</span><span class="string">"Description"</span><span class="special">)</span> <span class="special"><<</span> <span class="string">"'\n"</span><span class="special">;</span>
<span class="special">}</span>
</pre>
<p>
</p>
<p>
Since a lot of document traversal consists of finding the node/attribute
with the correct name, there are special functions for that purpose. For
example, <code class="computeroutput"><span class="identifier">child</span><span class="special">(</span><span class="string">"Tool"</span><span class="special">)</span></code>
returns the first node which has the name <code class="computeroutput"><span class="string">"Tool"</span></code>,
or null handle if there is no such node. This is an example of using such
functions (<a href="samples/traverse_base.cpp" target="_top">samples/traverse_base.cpp</a>):
</p>
<p>
</p>
<pre class="programlisting"><span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"Tool for *.dae generation: "</span> <span class="special"><<</span> <span class="identifier">tools</span><span class="special">.</span><span class="identifier">find_child_by_attribute</span><span class="special">(</span><span class="string">"Tool"</span><span class="special">,</span> <span class="string">"OutputFileMasks"</span><span class="special">,</span> <span class="string">"*.dae"</span><span class="special">).</span><span class="identifier">attribute</span><span class="special">(</span><span class="string">"Filename"</span><span class="special">).</span><span class="identifier">value</span><span class="special">()</span> <span class="special"><<</span> <span class="string">"\n"</span><span class="special">;</span>
<span class="keyword">for</span> <span class="special">(</span><span class="identifier">pugi</span><span class="special">::</span><span class="identifier">xml_node</span> <span class="identifier">tool</span> <span class="special">=</span> <span class="identifier">tools</span><span class="special">.</span><span class="identifier">child</span><span class="special">(</span><span class="string">"Tool"</span><span class="special">);</span> <span class="identifier">tool</span><span class="special">;</span> <span class="identifier">tool</span> <span class="special">=</span> <span class="identifier">tool</span><span class="special">.</span><span class="identifier">next_sibling</span><span class="special">(</span><span class="string">"Tool"</span><span class="special">))</span>
<span class="special">{</span>
<span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"Tool "</span> <span class="special"><<</span> <span class="identifier">tool</span><span class="special">.</span><span class="identifier">attribute</span><span class="special">(</span><span class="string">"Filename"</span><span class="special">).</span><span class="identifier">value</span><span class="special">()</span> <span class="special"><<</span> <span class="string">"\n"</span><span class="special">;</span>
<span class="special">}</span>
</pre>
<p>
</p>
<p>
Child node lists and attribute lists are simply double-linked lists; while
you can use <code class="computeroutput"><span class="identifier">previous_sibling</span></code>/<code class="computeroutput"><span class="identifier">next_sibling</span></code> and other such functions for
iteration, pugixml additionally provides node and attribute iterators, so
that you can treat nodes as containers of other nodes or attributes. All
iterators are bidirectional and support all usual iterator operations. The
iterators are invalidated if the node/attribute objects they're pointing
to are removed from the tree; adding nodes/attributes does not invalidate
any iterators.
</p>
<p>
Here is an example of using iterators for document traversal (<a href="samples/traverse_iter.cpp" target="_top">samples/traverse_iter.cpp</a>):
</p>
<p>
</p>
<pre class="programlisting"><span class="keyword">for</span> <span class="special">(</span><span class="identifier">pugi</span><span class="special">::</span><span class="identifier">xml_node_iterator</span> <span class="identifier">it</span> <span class="special">=</span> <span class="identifier">tools</span><span class="special">.</span><span class="identifier">begin</span><span class="special">();</span> <span class="identifier">it</span> <span class="special">!=</span> <span class="identifier">tools</span><span class="special">.</span><span class="identifier">end</span><span class="special">();</span> <span class="special">++</span><span class="identifier">it</span><span class="special">)</span>
<span class="special">{</span>
<span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"Tool:"</span><span class="special">;</span>
<span class="keyword">for</span> <span class="special">(</span><span class="identifier">pugi</span><span class="special">::</span><span class="identifier">xml_attribute_iterator</span> <span class="identifier">ait</span> <span class="special">=</span> <span class="identifier">it</span><span class="special">-></span><span class="identifier">attributes_begin</span><span class="special">();</span> <span class="identifier">ait</span> <span class="special">!=</span> <span class="identifier">it</span><span class="special">-></span><span class="identifier">attributes_end</span><span class="special">();</span> <span class="special">++</span><span class="identifier">ait</span><span class="special">)</span>
<span class="special">{</span>
<span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">" "</span> <span class="special"><<</span> <span class="identifier">ait</span><span class="special">-></span><span class="identifier">name</span><span class="special">()</span> <span class="special"><<</span> <span class="string">"="</span> <span class="special"><<</span> <span class="identifier">ait</span><span class="special">-></span><span class="identifier">value</span><span class="special">();</span>
<span class="special">}</span>
<span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span>
<span class="special">}</span>
</pre>
<p>
</p>
<p>
The methods described above allow traversal of immediate children of some
node; if you want to do a deep tree traversal, you'll have to do it via a
recursive function or some equivalent method. However, pugixml provides a
helper for depth-first traversal of a subtree. In order to use it, you have
to implement <code class="computeroutput"><span class="identifier">xml_tree_walker</span></code>
interface and to call <code class="computeroutput"><span class="identifier">traverse</span></code>
function.
</p>
<p>
This is an example of traversing tree hierarchy with xml_tree_walker (<a href="samples/traverse_walker.cpp" target="_top">samples/traverse_walker.cpp</a>):
</p>
<p>
</p>
<pre class="programlisting"><span class="keyword">struct</span> <span class="identifier">simple_walker</span><span class="special">:</span> <span class="identifier">pugi</span><span class="special">::</span><span class="identifier">xml_tree_walker</span>
<span class="special">{</span>
<span class="keyword">virtual</span> <span class="keyword">bool</span> <span class="identifier">for_each</span><span class="special">(</span><span class="identifier">pugi</span><span class="special">::</span><span class="identifier">xml_node</span><span class="special">&</span> <span class="identifier">node</span><span class="special">)</span>
<span class="special">{</span>
<span class="keyword">for</span> <span class="special">(</span><span class="keyword">int</span> <span class="identifier">i</span> <span class="special">=</span> <span class="number">0</span><span class="special">;</span> <span class="identifier">i</span> <span class="special"><</span> <span class="identifier">depth</span><span class="special">();</span> <span class="special">++</span><span class="identifier">i</span><span class="special">)</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">" "</span><span class="special">;</span> <span class="comment">// indentation
</span>
<span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">node_types</span><span class="special">[</span><span class="identifier">node</span><span class="special">.</span><span class="identifier">type</span><span class="special">()]</span> <span class="special"><<</span> <span class="string">": name='"</span> <span class="special"><<</span> <span class="identifier">node</span><span class="special">.</span><span class="identifier">name</span><span class="special">()</span> <span class="special"><<</span> <span class="string">"', value='"</span> <span class="special"><<</span> <span class="identifier">node</span><span class="special">.</span><span class="identifier">value</span><span class="special">()</span> <span class="special"><<</span> <span class="string">"'\n"</span><span class="special">;</span>
<span class="keyword">return</span> <span class="keyword">true</span><span class="special">;</span> <span class="comment">// continue traversal
</span> <span class="special">}</span>
<span class="special">};</span>
</pre>
<p>
</p>
<p>
</p>
<pre class="programlisting"><span class="identifier">simple_walker</span> <span class="identifier">walker</span><span class="special">;</span>
<span class="identifier">doc</span><span class="special">.</span><span class="identifier">traverse</span><span class="special">(</span><span class="identifier">walker</span><span class="special">);</span>
</pre>
<p>
</p>
<p>
Finally, for complex queries often a higher-level DSL is needed. pugixml
provides an implementation of XPath 1.0 language for such queries. The complete
description of XPath usage can be found in the manual, but here are some
examples:
</p>
<p>
</p>
<pre class="programlisting"><span class="identifier">pugi</span><span class="special">::</span><span class="identifier">xpath_node_set</span> <span class="identifier">tools</span> <span class="special">=</span> <span class="identifier">doc</span><span class="special">.</span><span class="identifier">select_nodes</span><span class="special">(</span><span class="string">"/Profile/Tools/Tool[@AllowRemote='true' and @DeriveCaptionFrom='lastparam']"</span><span class="special">);</span>
<span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"Tools:"</span><span class="special">;</span>
<span class="keyword">for</span> <span class="special">(</span><span class="identifier">pugi</span><span class="special">::</span><span class="identifier">xpath_node_set</span><span class="special">::</span><span class="identifier">const_iterator</span> <span class="identifier">it</span> <span class="special">=</span> <span class="identifier">tools</span><span class="special">.</span><span class="identifier">begin</span><span class="special">();</span> <span class="identifier">it</span> <span class="special">!=</span> <span class="identifier">tools</span><span class="special">.</span><span class="identifier">end</span><span class="special">();</span> <span class="special">++</span><span class="identifier">it</span><span class="special">)</span>
<span class="special">{</span>
<span class="identifier">pugi</span><span class="special">::</span><span class="identifier">xpath_node</span> <span class="identifier">node</span> <span class="special">=</span> <span class="special">*</span><span class="identifier">it</span><span class="special">;</span>
<span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">" "</span> <span class="special"><<</span> <span class="identifier">node</span><span class="special">.</span><span class="identifier">node</span><span class="special">().</span><span class="identifier">attribute</span><span class="special">(</span><span class="string">"Filename"</span><span class="special">).</span><span class="identifier">value</span><span class="special">();</span>
<span class="special">}</span>
<span class="identifier">pugi</span><span class="special">::</span><span class="identifier">xpath_node</span> <span class="identifier">build_tool</span> <span class="special">=</span> <span class="identifier">doc</span><span class="special">.</span><span class="identifier">select_single_node</span><span class="special">(</span><span class="string">"//Tool[contains(Description, 'build system')]"</span><span class="special">);</span>
<span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"\nBuild tool: "</span> <span class="special"><<</span> <span class="identifier">build_tool</span><span class="special">.</span><span class="identifier">node</span><span class="special">().</span><span class="identifier">attribute</span><span class="special">(</span><span class="string">"Filename"</span><span class="special">).</span><span class="identifier">value</span><span class="special">()</span> <span class="special"><<</span> <span class="string">"\n"</span><span class="special">;</span>
</pre>
<p>
</p>
<div class="caution"><table border="0" summary="Caution">
<tr>
<td rowspan="2" align="center" valign="top" width="25"><img alt="[Caution]" src="images/caution.png"></td>
<th align="left">Caution</th>
</tr>
<tr><td align="left" valign="top"><p>
XPath functions throw <code class="computeroutput"><span class="identifier">xpath_exception</span></code>
objects on error; the sample above does not catch these exceptions.
</p></td></tr>
</table></div>
</div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="quickstart.main.modify"></a><a class="link" href="quickstart.html#quickstart.main.modify" title="Modifying document data"> Modifying document data</a>
</h3></div></div></div>
<p>
The document in pugixml is fully mutable: you can completely change the document
structure and modify the data of nodes/attributes. All functions take care
of memory management and structural integrity themselves, so they always
result in structurally valid tree - however, it is possible to create an
invalid XML tree (for example, by adding two attributes with the same name
or by setting attribute/node name to empty/invalid string). Tree modification
is optimized for performance and for memory consumption, so if you have enough
memory you can create documents from scratch with pugixml and later save
them to file/stream instead of relying on error-prone manual text writing
and without too much overhead.
</p>
<p>
All member functions that change node/attribute data or structure are non-constant
and thus can not be called on constant handles. However, you can easily convert
constant handle to non-constant one by simple assignment: <code class="computeroutput"><span class="keyword">void</span>
<span class="identifier">foo</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">pugi</span><span class="special">::</span><span class="identifier">xml_node</span><span class="special">&</span> <span class="identifier">n</span><span class="special">)</span> <span class="special">{</span> <span class="identifier">pugi</span><span class="special">::</span><span class="identifier">xml_node</span> <span class="identifier">nc</span> <span class="special">=</span> <span class="identifier">n</span><span class="special">;</span> <span class="special">}</span></code>, so const-correctness
here mainly provides additional documentation.
</p>
<p>
As discussed before, nodes can have name and value, both of which are strings.
Depending on node type, name or value may be absent. You can use <code class="computeroutput"><span class="identifier">set_name</span></code> and <code class="computeroutput"><span class="identifier">set_value</span></code>
member functions to set them. Similar functions are available for attributes;
however, the <code class="computeroutput"><span class="identifier">set_value</span></code> function
is overloaded for some other types except strings, like floating-point numbers.
Also, attribute value can be set using an assignment operator. This is an
example of setting node/attribute name and value (<a href="samples/modify_base.cpp" target="_top">samples/modify_base.cpp</a>):
</p>
<p>
</p>
<pre class="programlisting"><span class="identifier">pugi</span><span class="special">::</span><span class="identifier">xml_node</span> <span class="identifier">node</span> <span class="special">=</span> <span class="identifier">doc</span><span class="special">.</span><span class="identifier">child</span><span class="special">(</span><span class="string">"node"</span><span class="special">);</span>
<span class="comment">// change node name
</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">node</span><span class="special">.</span><span class="identifier">set_name</span><span class="special">(</span><span class="string">"notnode"</span><span class="special">);</span>
<span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">", new node name: "</span> <span class="special"><<</span> <span class="identifier">node</span><span class="special">.</span><span class="identifier">name</span><span class="special">()</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span>
<span class="comment">// change comment text
</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">doc</span><span class="special">.</span><span class="identifier">last_child</span><span class="special">().</span><span class="identifier">set_value</span><span class="special">(</span><span class="string">"useless comment"</span><span class="special">);</span>
<span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">", new comment text: "</span> <span class="special"><<</span> <span class="identifier">doc</span><span class="special">.</span><span class="identifier">last_child</span><span class="special">().</span><span class="identifier">value</span><span class="special">()</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span>
<span class="comment">// we can't change value of the element or name of the comment
</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">node</span><span class="special">.</span><span class="identifier">set_value</span><span class="special">(</span><span class="string">"1"</span><span class="special">)</span> <span class="special"><<</span> <span class="string">", "</span> <span class="special"><<</span> <span class="identifier">doc</span><span class="special">.</span><span class="identifier">last_child</span><span class="special">().</span><span class="identifier">set_name</span><span class="special">(</span><span class="string">"2"</span><span class="special">)</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span>
</pre>
<p>
</p>
<p>
</p>
<pre class="programlisting"><span class="identifier">pugi</span><span class="special">::</span><span class="identifier">xml_attribute</span> <span class="identifier">attr</span> <span class="special">=</span> <span class="identifier">node</span><span class="special">.</span><span class="identifier">attribute</span><span class="special">(</span><span class="string">"id"</span><span class="special">);</span>
<span class="comment">// change attribute name/value
</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">attr</span><span class="special">.</span><span class="identifier">set_name</span><span class="special">(</span><span class="string">"key"</span><span class="special">)</span> <span class="special"><<</span> <span class="string">", "</span> <span class="special"><<</span> <span class="identifier">attr</span><span class="special">.</span><span class="identifier">set_value</span><span class="special">(</span><span class="string">"345"</span><span class="special">);</span>
<span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">", new attribute: "</span> <span class="special"><<</span> <span class="identifier">attr</span><span class="special">.</span><span class="identifier">name</span><span class="special">()</span> <span class="special"><<</span> <span class="string">"="</span> <span class="special"><<</span> <span class="identifier">attr</span><span class="special">.</span><span class="identifier">value</span><span class="special">()</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span>
<span class="comment">// we can use numbers or booleans
</span><span class="identifier">attr</span><span class="special">.</span><span class="identifier">set_value</span><span class="special">(</span><span class="number">1.234</span><span class="special">);</span>
<span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"new attribute value: "</span> <span class="special"><<</span> <span class="identifier">attr</span><span class="special">.</span><span class="identifier">value</span><span class="special">()</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span>
<span class="comment">// we can also use assignment operators for more concise code
</span><span class="identifier">attr</span> <span class="special">=</span> <span class="keyword">true</span><span class="special">;</span>
<span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"final attribute value: "</span> <span class="special"><<</span> <span class="identifier">attr</span><span class="special">.</span><span class="identifier">value</span><span class="special">()</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span>
</pre>
<p>
</p>
<p>
Nodes and attributes do not exist outside of document tree, so you can't
create them without adding them to some document. A node or attribute can
be created at the end of node/attribute list or before/after some other node.
All insertion functions return the handle to newly created object on success,
and null handle on failure. Even if the operation fails (for example, if
you're trying to add a child node to PCDATA node), the document remains in
consistent state, but the requested node/attribute is not added.
</p>
<div class="caution"><table border="0" summary="Caution">
<tr>
<td rowspan="2" align="center" valign="top" width="25"><img alt="[Caution]" src="images/caution.png"></td>
<th align="left">Caution</th>
</tr>
<tr><td align="left" valign="top"><p>
attribute() and child() functions do not add attributes or nodes to the
tree, so code like <code class="computeroutput"><span class="identifier">node</span><span class="special">.</span><span class="identifier">attribute</span><span class="special">(</span><span class="string">"id"</span><span class="special">)</span> <span class="special">=</span> <span class="number">123</span><span class="special">;</span></code> will not do anything if <code class="computeroutput"><span class="identifier">node</span></code> does not have an attribute with
name <code class="computeroutput"><span class="string">"id"</span></code>. Make sure
you're operating with existing attributes/nodes by adding them if necessary.
</p></td></tr>
</table></div>
<p>
This is an example of adding new attributes/nodes to the document (<a href="samples/modify_add.cpp" target="_top">samples/modify_add.cpp</a>):
</p>
<p>
</p>
<pre class="programlisting"><span class="comment">// add node with some name
</span><span class="identifier">pugi</span><span class="special">::</span><span class="identifier">xml_node</span> <span class="identifier">node</span> <span class="special">=</span> <span class="identifier">doc</span><span class="special">.</span><span class="identifier">append_child</span><span class="special">();</span>
<span class="identifier">node</span><span class="special">.</span><span class="identifier">set_name</span><span class="special">(</span><span class="string">"node"</span><span class="special">);</span>
<span class="comment">// add description node with text child
</span><span class="identifier">pugi</span><span class="special">::</span><span class="identifier">xml_node</span> <span class="identifier">descr</span> <span class="special">=</span> <span class="identifier">node</span><span class="special">.</span><span class="identifier">append_child</span><span class="special">();</span>
<span class="identifier">descr</span><span class="special">.</span><span class="identifier">set_name</span><span class="special">(</span><span class="string">"description"</span><span class="special">);</span>
<span class="identifier">descr</span><span class="special">.</span><span class="identifier">append_child</span><span class="special">(</span><span class="identifier">pugi</span><span class="special">::</span><span class="identifier">node_pcdata</span><span class="special">).</span><span class="identifier">set_value</span><span class="special">(</span><span class="string">"Simple node"</span><span class="special">);</span>
<span class="comment">// add param node before the description
</span><span class="identifier">pugi</span><span class="special">::</span><span class="identifier">xml_node</span> <span class="identifier">param</span> <span class="special">=</span> <span class="identifier">node</span><span class="special">.</span><span class="identifier">insert_child_before</span><span class="special">(</span><span class="identifier">pugi</span><span class="special">::</span><span class="identifier">node_element</span><span class="special">,</span> <span class="identifier">descr</span><span class="special">);</span>
<span class="identifier">param</span><span class="special">.</span><span class="identifier">set_name</span><span class="special">(</span><span class="string">"param"</span><span class="special">);</span>
<span class="comment">// add attributes to param node
</span><span class="identifier">param</span><span class="special">.</span><span class="identifier">append_attribute</span><span class="special">(</span><span class="string">"name"</span><span class="special">)</span> <span class="special">=</span> <span class="string">"version"</span><span class="special">;</span>
<span class="identifier">param</span><span class="special">.</span><span class="identifier">append_attribute</span><span class="special">(</span><span class="string">"value"</span><span class="special">)</span> <span class="special">=</span> <span class="number">1.1</span><span class="special">;</span>
<span class="identifier">param</span><span class="special">.</span><span class="identifier">insert_attribute_after</span><span class="special">(</span><span class="string">"type"</span><span class="special">,</span> <span class="identifier">param</span><span class="special">.</span><span class="identifier">attribute</span><span class="special">(</span><span class="string">"name"</span><span class="special">))</span> <span class="special">=</span> <span class="string">"float"</span><span class="special">;</span>
</pre>
<p>
</p>
<a name="xml_node::remove_attribute"></a><a name="xml_node::remove_child"></a><p>
If you do not want your document to contain some node or attribute, you can
remove it with <code class="computeroutput"><span class="identifier">remove_attribute</span></code>
and <code class="computeroutput"><span class="identifier">remove_child</span></code> functions.
Removing the attribute or node invalidates all handles to the same underlying
object, and also invalidates all iterators pointing to the same object. Removing
node also invalidates all past-the-end iterators to its attribute or child
node list. Be careful to ensure that all such handles and iterators either
do not exist or are not used after the attribute/node is removed.
</p>
<p>
This is an example of removing attributes/nodes from the document (<a href="samples/modify_remove.cpp" target="_top">samples/modify_remove.cpp</a>):
</p>
<p>
</p>
<pre class="programlisting"><span class="comment">// remove description node with the whole subtree
</span><span class="identifier">pugi</span><span class="special">::</span><span class="identifier">xml_node</span> <span class="identifier">node</span> <span class="special">=</span> <span class="identifier">doc</span><span class="special">.</span><span class="identifier">child</span><span class="special">(</span><span class="string">"node"</span><span class="special">);</span>
<span class="identifier">node</span><span class="special">.</span><span class="identifier">remove_child</span><span class="special">(</span><span class="string">"description"</span><span class="special">);</span>
<span class="comment">// remove id attribute
</span><span class="identifier">pugi</span><span class="special">::</span><span class="identifier">xml_node</span> <span class="identifier">param</span> <span class="special">=</span> <span class="identifier">node</span><span class="special">.</span><span class="identifier">child</span><span class="special">(</span><span class="string">"param"</span><span class="special">);</span>
<span class="identifier">param</span><span class="special">.</span><span class="identifier">remove_attribute</span><span class="special">(</span><span class="string">"value"</span><span class="special">);</span>
<span class="comment">// we can also remove nodes/attributes by handles
</span><span class="identifier">pugi</span><span class="special">::</span><span class="identifier">xml_attribute</span> <span class="identifier">id</span> <span class="special">=</span> <span class="identifier">param</span><span class="special">.</span><span class="identifier">attribute</span><span class="special">(</span><span class="string">"name"</span><span class="special">);</span>
<span class="identifier">param</span><span class="special">.</span><span class="identifier">remove_attribute</span><span class="special">(</span><span class="identifier">id</span><span class="special">);</span>
</pre>
<p>
</p>
</div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="quickstart.main.saving"></a><a class="link" href="quickstart.html#quickstart.main.saving" title="Saving document"> Saving document</a>
</h3></div></div></div>
<p>
Often after creating a new document or loading the existing one and processing
it, it is necessary to save the result back to file. Also it is occasionally
useful to output the whole document or a subtree to some stream; use cases
include debug printing, serialization via network or other text-oriented
medium, etc. pugixml provides several functions to output any subtree of
the document to a file, stream or another generic transport interface; these
functions allow to customize the output format, and also perform necessary
encoding conversions.
</p>
<p>
The node/attribute data is written to the destination properly formatted
according to the node type; all special XML symbols, such as < and &,
are properly escaped. In order to guard against forgotten node/attribute
names, empty node/attribute names are printed as <code class="computeroutput"><span class="string">":anonymous"</span></code>.
For proper output, make sure all node and attribute names are set to meaningful
values.
</p>
<p>
If you want to save the whole document to a file, you can use the <code class="computeroutput"><span class="identifier">save_file</span></code> function, which returns <code class="computeroutput"><span class="keyword">true</span></code> on success. This is a simple example
of saving XML document to file (<a href="samples/save_file.cpp" target="_top">samples/save_file.cpp</a>):
</p>
<p>
</p>
<pre class="programlisting"><span class="comment">// save document to file
</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"Saving result: "</span> <span class="special"><<</span> <span class="identifier">doc</span><span class="special">.</span><span class="identifier">save_file</span><span class="special">(</span><span class="string">"save_file_output.xml"</span><span class="special">)</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span>
</pre>
<p>
</p>
<p>
For additional interoperability pugixml provides functions for saving document
to any object which implements C++ std::ostream interface. This allows you
to save documents to any standard C++ stream (i.e. file stream) or any third-party
compliant implementation (i.e. Boost Iostreams). Most notably, this allows
for easy debug output, since you can use <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span></code>
stream as saving target. There are two functions, one works with narrow character
streams, another handles wide character ones.
</p>
<p>
This is a simple example of saving XML document to standard output (<a href="samples/save_stream.cpp" target="_top">samples/save_stream.cpp</a>):
</p>
<p>
</p>
<pre class="programlisting"><span class="comment">// save document to standard output
</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"Document:\n"</span><span class="special">;</span>
<span class="identifier">doc</span><span class="special">.</span><span class="identifier">save</span><span class="special">(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span><span class="special">);</span>
</pre>
<p>
</p>
<p>
All of the above saving functions are implemented in terms of writer interface.
This is a simple interface with a single function, which is called several
times during output process with chunks of document data as input. In order
to output the document via some custom transport, for example sockets, you
should create an object which implements <code class="computeroutput"><span class="identifier">xml_writer_file</span></code>
interface and pass it to <code class="computeroutput"><span class="identifier">xml_document</span><span class="special">::</span><span class="identifier">save</span></code>
function.
</p>
<p>
This is a simple example of custom writer for saving document data to STL
string (<a href="samples/save_custom_writer.cpp" target="_top">samples/save_custom_writer.cpp</a>);
read the sample code for more complex examples:
</p>
<p>
</p>
<pre class="programlisting"><span class="keyword">struct</span> <span class="identifier">xml_string_writer</span><span class="special">:</span> <span class="identifier">pugi</span><span class="special">::</span><span class="identifier">xml_writer</span>
<span class="special">{</span>
<span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span> <span class="identifier">result</span><span class="special">;</span>
<span class="keyword">virtual</span> <span class="keyword">void</span> <span class="identifier">write</span><span class="special">(</span><span class="keyword">const</span> <span class="keyword">void</span><span class="special">*</span> <span class="identifier">data</span><span class="special">,</span> <span class="identifier">size_t</span> <span class="identifier">size</span><span class="special">)</span>
<span class="special">{</span>
<span class="identifier">result</span> <span class="special">+=</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span><span class="special">(</span><span class="keyword">static_cast</span><span class="special"><</span><span class="keyword">const</span> <span class="keyword">char</span><span class="special">*>(</span><span class="identifier">data</span><span class="special">),</span> <span class="identifier">size</span><span class="special">);</span>
<span class="special">}</span>
<span class="special">};</span>
</pre>
<p>
</p>
<p>
While the previously described functions saved the whole document to the
destination, it is easy to save a single subtree. Instead of calling <code class="computeroutput"><span class="identifier">xml_document</span><span class="special">::</span><span class="identifier">save</span></code>, just call <code class="computeroutput"><span class="identifier">xml_node</span><span class="special">::</span><span class="identifier">print</span></code>
function on the target node. You can save node contents to C++ IOstream object
or custom writer in this way. Saving a subtree slightly differs from saving
the whole document; read the manual for more information.
</p>
</div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="quickstart.main.feedback"></a><a class="link" href="quickstart.html#quickstart.main.feedback" title="Feedback"> Feedback</a>
</h3></div></div></div>
<p>
If you believe you've found a bug in pugixml, please file an issue via <a href="http://code.google.com/p/pugixml/issues/entry" target="_top">issue submission form</a>.
Be sure to include the relevant information so that the bug can be reproduced:
the version of pugixml, compiler version and target architecture, the code
that uses pugixml and exhibits the bug, etc. Feature requests and contributions
can be filed as issues, too.
</p>
<a name="email"></a><p>
If filing an issue is not possible due to privacy or other concerns, you
can contact pugixml author by e-mail directly: <a href="mailto:arseny.kapoulkine@gmail.com" target="_top">arseny.kapoulkine@gmail.com</a>.
</p>
</div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="quickstart.main.license"></a><a class="link" href="quickstart.html#quickstart.main.license" title="License"> License</a>
</h3></div></div></div>
<p>
The pugixml library is distributed under the MIT license:
</p>
<div class="blockquote"><blockquote class="blockquote">
<p>
Copyright (c) 2006-2010 Arseny Kapoulkine
</p>
<p>
Permission is hereby granted, free of charge, to any person obtaining a
copy of this software and associated documentation files (the "Software"),
to deal in the Software without restriction, including without limitation
the rights to use, copy, modify, merge, publish, distribute, sublicense,
and/or sell copies of the Software, and to permit persons to whom the Software
is furnished to do so, subject to the following conditions:
</p>
<p>
The above copyright notice and this permission notice shall be included
in all copies or substantial portions of the Software.
</p>
<p>
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
IN THE SOFTWARE.
</p>
</blockquote></div>
</div>
</div>
<div class="footnotes">
<br><hr width="100" align="left">
<div class="footnote"><p><sup>[<a name="ftn.trademarks" href="#trademarks" class="para">1</a>] </sup>All trademarks used are properties of their
respective owners.</p></div>
</div>
</div>
<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
<td align="left"><p><small>Last revised: July 15, 2010 at 17:02:03 GMT</small></p></td>
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